Increasing demands for high data-rate, high-performance wireless transmission has motivated current and evolving wireless standards towards the use of multiple antennas at both a transmitter and a receiver of a communications device of a communications system. The use of multiple transmit and receive antennas may be referred to as MIMO, adaptive antenna systems (AAS), and so forth.
Generally, MIMO technology relies on coherent detection which necessitates estimating a channel between each transmit-receiver antenna pair. Estimating the channel(s) may require a substantial number of pilots to provide a good channel estimate. In practice, only a minimal number of pilots are included in a transmission since the presence of the pilots take away valuable bandwidth. Therefore, the communications system often relies on integrating pilot energy over multiple symbols to get a desired degree of channel estimation accuracy.
In communications systems, the integration time may be limited by the rate of variation of the channel. The rate of variation may cause significant errors in the channel estimate as a mobility of a communications device increases, i.e., a highly mobile communications device may have a high rate of variation, thereby potentially leading to significant errors in the channel estimates.
Another technique that may be used to estimate the channels is commonly referred to as blind techniques, sometimes also referred to as joint channel-symbol estimation techniques, in order to provide an estimate of the channel based on a previously received transmission. Again, noise and outdated data, especially when the channel is changing fast (due to a highly mobile communications device, for example), are inevitable problems which might cause significant channel estimation errors. These errors may lead to significant performance degradation using the conventional coherent detection approach.